Preserving, From Resource Management Adjustment, Portions Of An Overcommitted Resource Managed By A Hypervisor

ABSTRACT

Methods, apparatuses, and computer program products for preserving, from resource management adjustment, portions of an overcommitted resource managed by a hypervisor are provided. Embodiments include identifying, by the hypervisor, a privileged guest from among a plurality of guests of the hypervisor; identifying, by the hypervisor, portions of the overcommitted resource that are allocated to the privileged guest; and preventing, by the hypervisor, resource management adjustment to the identified portions of the overcommitted resource that are allocated to the privileged guest.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of and claims priorityfrom U.S. patent application Ser. No. 13/212,516, filed on Aug. 18,2011.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The field of the invention is data processing, or, more specifically,methods, apparatuses, and computer program products for preserving, fromresource management adjustment, portions of an overcommitted resourcemanaged by a hypervisor.

2. Description of Related Art

The development of the EDVAC computer system of 1948 is often cited asthe beginning of the computer era. Since that time, computer systemshave evolved into extremely complicated devices. Today's computers aremuch more sophisticated than early systems such as the EDVAC. Computersystems typically include a combination of hardware and softwarecomponents, application programs, operating systems, processors, buses,memory, input/output devices, and so on. As advances in semiconductorprocessing and computer architecture push the performance of thecomputer higher and higher, more sophisticated computer software hasevolved to take advantage of the higher performance of the hardware,resulting in computer systems today that are much more powerful thanjust a few years ago.

One area in which computer software has evolved to take advantage ofhigh performance hardware is the set of software tools referred to ashypervisors. A hypervisor is a layer of system software that runs on thecomputer hardware beneath an operating system layer to allow multipleoperating systems to run, unmodified, on a host computer at the sametime by providing each operating system with a set of virtual resources.These virtual resources provide each operating system a portion of theactual resources of the computer. Resources, such as a processor, may beimplemented as time slices of the total time the resource is availablefor use. Other resources, such as memory, may be divided among multipleguest operating systems, where each guest is allocated an instance ofmemory. Using a hypervisor, the distribution of computer resourceswithin a single computer makes the computer appear to function as if itwere two or more independent computers.

To ensure maximum utilization of resources, often hypervisorsover-commit a resource to guest operating systems. For example, if ahypervisor creates the illusion that there are more instances (orbandwidth) of a resource than actually physically available, thatresource is considered to be overcommitted. In an overcommitted resourceenvironment, the hypervisor may balance the demands of the guestoperating systems by performing resource management adjustments. Inresponse to a resource management adjustment, the speed and efficiencyof a particular guest operating system may be diminished.

SUMMARY OF THE INVENTION

Methods, apparatuses, and computer program products for preserving, fromresource management adjustment, portions of an overcommitted resourcemanaged by a hypervisor are provided. Embodiments include identifying,by the hypervisor, a privileged guest from among a plurality of guestsof the hypervisor; identifying, by the hypervisor, portions of theovercommitted resource that are allocated to the privileged guest; andpreventing, by the hypervisor, resource management adjustment to theidentified portions of the overcommitted resource that are allocated tothe privileged guest.

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescriptions of exemplary embodiments of the invention as illustrated inthe accompanying drawings wherein like reference numbers generallyrepresent like parts of exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 sets forth a diagram of automated computing machinery comprisingan exemplary computer useful in preserving, from resource managementadjustment, portions of an overcommitted resource managed by ahypervisor according to embodiments of the present invention.

FIG. 2 sets forth a diagram illustrating an exemplary computerconfigured with a hypervisor useful in preserving, from resourcemanagement adjustment, portions of an overcommitted resource managed bya hypervisor according to embodiments of the present invention.

FIG. 3 sets forth a flow chart illustrating an exemplary method forpreserving, from resource management adjustment, portions of anovercommitted resource managed by a hypervisor according to embodimentsof the present invention.

FIG. 4 sets forth a flow chart illustrating a further exemplary methodfor preserving, from resource management adjustment, portions of anovercommitted resource managed by a hypervisor according to embodimentsof the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Exemplary methods, apparatus, and products for preserving, from resourcemanagement adjustment, portions of an overcommitted resource managed bya hypervisor in accordance with the present invention are described withreference to the accompanying drawings, beginning with FIG. 1.Preserving, from resource management adjustment, portions of anovercommitted resource managed by a hypervisor in accordance with thepresent invention is generally implemented with computers, that is, withautomated computing machinery.

FIG. 1 sets forth a block diagram of automated computing machinerycomprising an exemplary computer (152) useful in preserving, fromresource management adjustment, portions of an overcommitted resourcemanaged by a hypervisor according to embodiments of the presentinvention. The computer (152) of FIG. 1 includes at least one computerprocessor (156) or ‘CPU’ as well as random access memory (168) (RAM')which is connected through a high speed memory bus (166) and bus adapter(158) to the processor (156) and to other components of the computer(152).

Stored in RAM (168) is a hypervisor (111), an operating system (108), anon-privileged guest operating system (117), and a privileged guestoperating system (192), and applications (106, 107, 191). The hypervisor(111) stored in RAM (168) is a layer of system software that runs on thecomputer hardware beneath an operating system layer to allows multipleoperating systems to run, unmodified, on a host computer at the sametime. The hypervisor (111) provides each operating system with a set ofvirtual resources by allocating these resources to each operating systemusing logical partitions. A logical partition (‘LPAR’)—sometimesreferred to as a ‘virtual machine’—is a set of data structures andservices that enables distribution of computer resources within a singlecomputer to make the computer function as if it were two or moreindependent computers.

In order to allow multiple operating systems to run at the same time,the hypervisor (111) assigns virtual processors (115) to each operatingsystem (108, 117, 192) and schedules virtual processors (115) on thephysical processors of the computer (152). A virtual processor is asubsystem that implements assignment of processor time to a logicalpartition. In the example of FIG. 1, one processor (156) is illustrated,however, according to embodiments of the present invention, a sharedpool of physical processors may support the assignment of partialphysical processors (in time slices) to a logical partition. Suchpartial physical processors shared in time slices are referred to as‘virtual processors.’ A thread of execution is said to run on a virtualprocessor when it is running on the virtual processor's time slice.Sub-processor partitions time-share a physical processor among a set ofvirtual processors, in a manner that is invisible to an operating systemrunning in a logical partition. Unlike multiprogramming within theoperating system where a thread can remain in control of the physicalprocessor by running in interrupt-disabled mode, in sub-processorpartitions, the thread is still pre-empted by the hypervisor at the endof its virtual processor's time slice, in order to make the physicalprocessor available to a different virtual processor.

In the example of FIG. 1, the hypervisor (111) allocates virtualresources to a logical partition (103) that provides an executionenvironment for application (106) and operating system (108). Thehypervisor (111) also allocates virtual resources to a logical partition(105) that provides an execution environment for application (107) andnon-privileged guest operating system (117). In addition, the hypervisor(111) also allocates virtual resources to a logical partition (190) thatprovides an execution environment for application (191) and privilegedguest operating system (192). Each application (106, 107, 191) is a setof computer program instructions implementing user-level dataprocessing. Each application (106, 107, 191) may be a stand-aloneapplication in which all the computer program instructions of eachapplication (106, 107, 191) are executed on a single compute node, oreach application (106, 107, 191) may be a distributed application inwhich portions of the computer program instructions are executedserially or in parallel with other portions of the computer programinstructions being executed on other compute nodes.

A guest operating system is an operating system that is limited to theresources and abstractions provided by a hypervisor. In thisspecification, a guest operating system is considered ‘privileged’ inthat it is specially designated due to the nature of its executionapplications or its function. That is, a privileged guest operatingsystem may be so designated because it is responsible for executing timecritical applications. In the example of FIG. 1, the non-privilegedguest operating system (117) controls the execution of the application(107) on the computer (152) and the privileged guest operating system(192) controls execution of application (191) on the computer (152). Thenon-privileged guest operating system (117) of FIG. 1 is system softwarethat manages the virtual resources allocated to the logical partition(105) by the hypervisor (111) and the privileged guest operating system(192) is system software that manages the virtual resources allocated tothe logical partition (190) by the hypervisor (111). The non-privilegedguest operating system (117) and the privileged guest operating system(192) perform basic tasks such as, for example, controlling andallocating virtual memory, prioritizing the processing of instructions,controlling virtualized input and output devices, facilitatingnetworking, and managing a virtualized file system.

Similarly, the operating system (108) of FIG. 1 controls the executionof the application (106) on the computer (152). The application (106) ofFIG. 1 accesses resources provided by the operating system (108) throughthe kernel (109). The kernel (109) is the core component of theoperating system (108) that manages the system's resources and thecommunication between applications and virtual resources provided by thehypervisor (111). The kernel (109) provides software applications withabstraction layers of the virtual hardware resources that allow theapplications to utilize these virtual hardware resources. The kernel(109) makes these abstraction layers available to user-levelapplications through inter-process communication mechanisms.

The hypervisor (111) is configured for preserving, from resourcemanagement adjustment, portions of an overcommitted resource managed bya hypervisor according to embodiments of the present invention.Specifically, the hypervisor (111) includes computer programinstructions that when executed by the processor (156), cause thecomputer (152) to carry out the steps of: identifying, by the hypervisor(111), a privileged guest (192) from among a plurality of guests (192,117) of the hypervisor (111); identifying, by the hypervisor (111),portions of the overcommitted resource that are allocated to theprivileged guest (192); and preventing, by the hypervisor (111),resource management adjustment to the identified portions of theovercommitted resource that are allocated to the privileged guest (192).

The applications (106, 107, 191), the operating systems (108, 117, 192),the kernel (109), and the hypervisor (111) illustrated in FIG. 1 aresoftware components, that is computer program instructions. Operatingsystems that may be improved for providing policy-based operating systemservices in a hypervisor on a computing system in accordance with thepresent invention may include UNIX™, Linux™, Microsoft NT™, IBM's AIX™,IBM's i5/OS™, and others as will occur to those of skill in the art. Theoperating systems (108, 117, 192), the applications (106, 107, 191), thelogical partitions (103, 105, 190), and the hypervisor (111) in theexample of FIG. 1 are shown in RAM (168), but many components of suchsoftware typically are stored in non-volatile memory also, for example,on a disk drive (170).

The computer (152) of FIG. 1 includes disk drive adapter (172) coupledthrough expansion bus (160) and bus adapter (158) to processor (156) andother components of the computer (152). Disk drive adapter (172)connects non-volatile data storage to the computer (152) in the form ofdisk drive (170). Disk drive adapters useful in computers forpreserving, from resource management adjustment, portions of anovercommitted resource managed by a hypervisor according to embodimentsof the present invention include Integrated Drive Electronics (‘IDE’)adapters, Small Computer System Interface (‘SCSI’) adapters, and othersas will occur to those of skill in the art. Non-volatile computer memoryalso may be implemented for as an optical disk drive, electricallyerasable programmable read-only memory (so-called ‘EEPROM’ or ‘Flash’memory), RAM drives, and so on, as will occur to those of skill in theart.

The example computer (152) of FIG. 1 includes one or more input/output(‘I/O’) adapters (178). I/O adapters implement user-orientedinput/output through, for example, software drivers and computerhardware for controlling output to display devices such as computerdisplay screens, as well as input from a user (101) on user inputdevices (181) such as keyboards and mice. The example computer (152) ofFIG. 1 includes a video adapter (183), which is an example of an I/Oadapter specially designed for graphic output to a display device (180)such as a display screen or computer monitor. Video adapter (183) isconnected to processor (156) through a high speed video bus (164), busadapter (158), and the front side bus (162), which is also a high speedbus.

The exemplary computer (152) of FIG. 1 includes a communications adapter(167) for data communications with other computers (182) and for datacommunications with a data communications network (100). Such datacommunications may be carried out serially through RS-232 connections,through external buses such as a Universal Serial Bus (‘USB’), throughdata communications networks such as IP data communications networks,and in other ways as will occur to those of skill in the art.Communications adapters implement the hardware level of datacommunications through which one computer sends data communications toanother computer, directly or through a data communications network.Examples of communications adapters useful for preserving, from resourcemanagement adjustment, portions of an overcommitted resource managed bya hypervisor according to embodiments of the present invention includemodems for wired dial-up communications, Ethernet (IEEE 802.3) adaptersfor wired data communications network communications, and 802.11adapters for wireless data communications network communications.

For further explanation of allocating virtual processors to logicalpartitions by the hypervisor, FIG. 2 sets forth a diagram illustratingan exemplary computer configured with a hypervisor useful in preserving,from resource management adjustment, portions of an overcommittedresource managed by a hypervisor according to embodiments of the presentinvention.

The system of FIG. 2 includes logical partition (LPAR) (202) and LPAR(204). The system of FIG. 2 includes two operating systems (206, 208),one each in LPAR (202) and LPAR (204) respectively. The system of FIG. 2includes six logical processors (220-225), two for operating system(206) in LPAR (202) and four for operating system (208) in LPAR (204). Alogical processor is an operating system's structure for schedulingthreads for execution. It represents a portion of the resources of aprocessor that is capable of carrying out the execution of a thread. Sixthreads (210-215) run on the six logical processors (220-225)respectively, one thread per logical processor. The system of FIG. 2includes a hypervisor (111) and four virtual processors, two virtualprocessors (230, 231) assigned to LPAR (202) and two virtual processors(232, 233) assigned to LPAR (204).

The system of FIG. 2 also includes three physical processors (240, 242,244). In the examples in this specification, the physical processors(240, 242, 244) are shared according to processing units with 1.0processing units representing the processing capacity of one physicalprocessor. In this example, the processing capacity of the threephysical processors (240, 242, 244) is apportioned to the LPARs asfollows:

-   -   All of the processing capacity of physical processor (240) is        assigned entirely to virtual processor (230), so that logical        processor (220) has available to it the entirety of physical        processor (240).    -   One-half the processing capacity of physical processor (242) is        assigned to virtual processor (231), so that logical processor        (221) has available to it in time slices one-half of physical        processor (242).    -   One-half the processing capacity of physical processor (242) is        assigned to virtual processor (232). Virtual processor (232) is        assigned to LPAR (204) which runs in simultaneous multithreading        mode with two logical processors (222, 223) for virtual        processor (232). Logical processor (222) and logical processor        (223) each has available to it in time slices one-fourth of the        processing capacity of physical processor (242).    -   All of the processing capacity of physical processor (244) is        assigned to virtual processor (233). Virtual processor (233) is        assigned to LPAR (204) which runs in simultaneous multithreading        mode with two logical processors (224, 225) for virtual        processor (233). Logical processor (224) and logical processor        (225) each has available to it in time slices one-half of the        processing capacity of physical processor (244).

The number, arrangement, and assignments of physical processors, virtualprocessors, and logical processors in the system of FIG. 2 are forexplanation only, and not for a limitation of the present invention. Acomputer useful for preserving, from resource management adjustment,portions of an overcommitted resource managed by a hypervisor accordingto embodiments of the present invention may support a multiplicity oflogical partitions and may include any number, arrangement, orassignment of physical processors, virtual processors, and logicalprocessors.

For further explanation, FIG. 3 sets forth a flow chart illustrating anexemplary method for preserving, from resource management adjustment,portions of an overcommitted resource managed by a hypervisor accordingto embodiments of the present invention. The method of FIG. 3 includesidentifying (302), by the hypervisor (111), a privileged guest (340)from among a plurality (350) of guests of the hypervisor (111).Identifying (302) a privileged guest (340) from among a plurality (350)of guests of the hypervisor (111) may be carried out by examining thepriorities of the guest operating systems; determining which guestoperating systems are executing time sensitive or critical applications;determining which guest operating systems most require predictableperformance; or a guest operating system is identified as a privilegedguest operating system by the user or system administrator.

The method of FIG. 3 includes identifying (304), by the hypervisor(111), portions (322) of the overcommitted resource (320) that areallocated to the privileged guest (340). An overcommitted resource maybe any resource of the computer that is divided into assigned portionsgreater than the whole of all of the portions of the resource. Resourcesmay include memory, processors, and input/output (I/O) devices. Examplesof over-committing resources include assigning the same section ofmemory to multiple guest operating systems. Identifying (304) portions(322) of the overcommitted resource (320) that are allocated to theprivileged guest (340) may be carried out by tracking within thehypervisor (111) assignments of the portions of the overcommittedresource (320) to the different guest operating systems. For example,the non-privileged guest operating system (344) may be allocated a firstportion (324) of the overcommitted resource (320) and a privileged guest(340) may be allocated a second portion (322) of the overcommittedresource (320).

The method of FIG. 3 includes preventing (306), by the hypervisor (111),resource management adjustment to the identified portions (322) of theovercommitted resource (320) that are allocated to the privileged guest(340). A resource management adjustment is an action taken by ahypervisor in response to over utilization of an overcommitted resource.For example, if memory is overcommitted (i.e., the same portions ofmemory are assigned to multiple guest operating systems) and themultiple guest operating systems begin to approach full utilization oftheir allocated portions of memory, the hypervisor (111) may need toreduce the amount of memory that is assigned to each guest operatingsystem. Preventing (306) resource management adjustment to theidentified portions (322) of the overcommitted resource (320) that areallocated to the privileged guest (340) may be carried out by performingthe resource management adjustment on one or more of the guest operatingsystems that are not identified as a privileged guest operating system.

For further explanation, FIG. 4 sets forth a flow chart illustrating afurther exemplary method for preserving, from resource managementadjustment, portions of an overcommitted resource managed by ahypervisor according to embodiments of the present invention. The methodof FIG. 4 is similar to the method of FIG. 3 in that the method of FIG.4 also includes: identifying (302), by the hypervisor (111), aprivileged guest (340) from among a plurality (350) of guests of thehypervisor (111); identifying (304), by the hypervisor (111), portions(322) of the overcommitted resource (320) that are allocated to theprivileged guest (340); and preventing (306), by the hypervisor (111),resource management adjustment to the identified portions (322) of theovercommitted resource (320) that are allocated to the privileged guest(340).

In the method of FIG. 4, preventing (306) resource management adjustmentto the identified portions (322) of the overcommitted resource (320)that are allocated to the privileged guest (340) optionally includesmarking (402) as non-swappable, by the hypervisor (111), memory pagesallocated to the identified privileged guest (340). The resourcemanagement adjustment of swapping memory includes taking pages fromwithin memory and storing the pages in a secondary storage, thus freeingup space with memory. Marking (402) as non-swappable memory pagesallocated to the identified privileged guest (340) may be carried out bytracking the pages that correspond to the privileged guest (340) andonly allowing swapping out pages that are not associated with theprivileged guest (340).

Normally, when the hypervisor wants to reclaim memory, it transmits aballoon request to a balloon driver within a guest operating system. Theballoon driver responds by allocating pinned physical pages within theguest operating system using appropriate native interfaces.

Inflating the balloon increases memory pressure in the guest operatingsystem, causing it to invoke its own native memory managementalgorithms. When memory is plentiful, the guest operating system willreturn memory from its free list. When memory within the guest operatingsystem is scarce, it must reclaim space to satisfy the driver allocationrequest. The guest operating system decides which particular pages toreclaim and, if necessary, pages them out to its own virtual disk. Theballoon driver communicates the physical page number for each allocatedpage to the hypervisor, which may then reclaim the corresponding machinepage. Deflating the balloon frees up memory for general use within theguest operating system.

In the method of FIG. 4, preventing (306) resource management adjustmentto the identified portions (322) of the overcommitted resource (320)that are allocated to the privileged guest (340) optionally includespreventing (404), by the hypervisor (111), issuance of a memory balloonrequest to the identified privileged guest (340). Preventing (404), bythe hypervisor (111), issuance of a memory balloon request to theidentified privileged guest (340) may be carried out by transmittingmemory balloon inflation requests to other guest operating systems thatare not identified as a “privileged guest operating system.”

In the method of FIG. 4, preventing (306) resource management adjustmentto the identified portions (322) of the overcommitted resource (320)that are allocated to the privileged guest (340) optionally includespreventing (406), by the hypervisor (111), migration of the identifiedprivileged guest. The resource management adjustment by migrating guestinclude, reallocating a one guest operating system from one physicalmachine to another physical machine. Preventing (406), by the hypervisor(111), migration of the identified privileged guest may be carried outby tracking the privileged guest and preventing reallocation of the sameat the start of the migration process.

In the method of FIG. 4, preventing (306) resource management adjustmentto the identified portions (322) of the overcommitted resource (320)that are allocated to the privileged guest (340) optionally includespreventing (408), by the hypervisor (111), reallocation to other guests,of processor bandwidth reserved for execution of the identifiedprivileged guest (340). Preventing (408), by the hypervisor (111),reallocation to other guests, of processor bandwidth reserved forexecution of the identified privileged guest (340) may be carried out bytracking the processor bandwidth that is assigned to privileged guestoperating systems and preventing reallocation of that bandwidth to otherguest operating systems.

In the method of FIG. 4, preventing (306) resource management adjustmentto the identified portions (322) of the overcommitted resource (320)that are allocated to the privileged guest (340) optionally includespreventing (410), by the hypervisor (111), reallocation to other guests,of input/output (I/O) or network device bandwidth reserved for use bythe identified privileged guest (340). Preventing (410), by thehypervisor (111), reallocation to other guests, of input/output (I/O) ornetwork device bandwidth reserved for use by the identified privilegedguest (340) may be carried out by tracking the I/O or network devicebandwidth that is assigned to privileged guest operating systems andpreventing reallocation of that bandwidth to other guest operatingsystems.

Exemplary embodiments of the present invention are described largely inthe context of a fully functional computer system for preserving, fromresource management adjustment, portions of an overcommitted resourcemanaged by a hypervisor. Readers of skill in the art will recognize,however, that the present invention also may be embodied in a computerprogram product disposed upon computer readable storage media for usewith any suitable data processing system. Such computer readable storagemedia may be any storage medium for machine-readable information,including magnetic media, optical media, or other suitable media.Examples of such media include magnetic disks in hard drives ordiskettes, compact disks for optical drives, magnetic tape, and othersas will occur to those of skill in the art. Persons skilled in the artwill immediately recognize that any computer system having suitableprogramming means will be capable of executing the steps of the methodof the invention as embodied in a computer program product. Personsskilled in the art will recognize also that, although some of theexemplary embodiments described in this specification are oriented tosoftware installed and executing on computer hardware, nevertheless,alternative embodiments implemented as firmware or as hardware are wellwithin the scope of the present invention.

As will be appreciated by one skilled in the art, aspects of the presentinvention may be embodied as a system, method or computer programproduct. Accordingly, aspects of the present invention may take the formof an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc.) or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module” or “system.”Furthermore, aspects of the present invention may take the form of acomputer program product embodied in one or more computer readablemedium(s) having computer readable program code embodied thereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readable signalmedium or a computer readable storage medium. A computer readablestorage medium may be, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system,apparatus, or device, or any suitable combination of the foregoing. Morespecific examples (a non-exhaustive list) of the computer readablestorage medium would include the following: an electrical connectionhaving one or more wires, a portable computer diskette, a hard disk, arandom access memory (RAM), a read-only memory (ROM), an erasableprogrammable read-only memory (EPROM or Flash memory), an optical fiber,a portable compact disc read-only memory (CD-ROM), an optical storagedevice, a magnetic storage device, or any suitable combination of theforegoing. In the context of this document, a computer readable storagemedium may be any tangible medium that can contain, or store a programfor use by or in connection with an instruction execution system,apparatus, or device.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium may be any computer readable medium thatis not a computer readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wireline, optical fiber cable, RF, etc., or any suitable combination ofthe foregoing.

Computer program code for carrying out operations for aspects of thepresent invention may be written in any combination of one or moreprogramming languages, including an object oriented programming languagesuch as Java, Smalltalk, C++ or the like and conventional proceduralprogramming languages, such as the “C” programming language or similarprogramming languages. The program code may execute entirely on theuser's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on a remotecomputer or entirely on the remote computer or server. In the latterscenario, the remote computer may be connected to the user's computerthrough any type of network, including a local area network (LAN) or awide area network (WAN), or the connection may be made to an externalcomputer (for example, through the Internet using an Internet ServiceProvider).

Aspects of the present invention are described above with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems) and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor of a general purpose computer, specialpurpose computer, or other programmable data processing apparatus toproduce a machine, such that the instructions, which execute via theprocessor of the computer or other programmable data processingapparatus, create means for implementing the functions/acts specified inthe flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof code, which comprises one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblock may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

It will be understood from the foregoing description that modificationsand changes may be made in various embodiments of the present inventionwithout departing from its true spirit. The descriptions in thisspecification are for purposes of illustration only and are not to beconstrued in a limiting sense. The scope of the present invention islimited only by the language of the following claims.

1. A method of preserving, from resource management adjustment, portions of an overcommitted resource managed by a hypervisor, the method comprising: identifying, by the hypervisor, a privileged guest from among a plurality of guests of the hypervisor; identifying, by the hypervisor, portions of the overcommitted resource that are allocated to the privileged guest; and preventing, by the hypervisor, resource management adjustment to the identified portions of the overcommitted resource that are allocated to the privileged guest.
 2. The method of claim 1 wherein preventing resource management adjustment to the identified portions of the overcommitted resource that are allocated to the privileged guest includes marking as non-swappable, by the hypervisor, memory pages allocated to the identified privileged guest.
 3. The method of claim 1 wherein preventing resource management adjustment to the identified portions of the overcommitted resource that are allocated to the privileged guest includes preventing, by the hypervisor, issuance of a memory balloon request to the identified privileged guest.
 4. The method of claim 1 wherein preventing resource management adjustment to the identified portions of the overcommitted resource that are allocated to the privileged guest includes preventing, by the hypervisor, migration of the identified privileged guest.
 5. The method of claim 1 wherein preventing resource management adjustment to the identified portions of the overcommitted resource that are allocated to the privileged guest includes preventing, by the hypervisor, reallocation to other guests, of processor bandwidth reserved for execution of the identified privileged guest.
 6. The method of claim 1 wherein preventing resource management adjustment to the identified portions of the overcommitted resource that are allocated to the privileged guest includes preventing, by the hypervisor, reallocation to other guests, of input/output (I/O) or network device bandwidth reserved for use by the identified privileged guest. 7-18. (canceled) 